1. Field of the Invention
The present invention relates generally to a load force resisting corrugated assembly, and specifically to a pallet or dunnage support constructed of corrugated paperboard that minimizes adverse environmental impact, occupies little space before it is configured, and effectively saves production, storage and transportation costs. The present corrugated paperboard assembly can be shipped and stored as either one or more die-cut and scored corrugated paperboard pieces, thereby eliminating excess volume, with the pieces being readily interconnectable to form a complete pallet or dunnage support assembly. In preferred form, two or more of these pieces are nested and glued together to form an assembly. Further, it is preferable that the paperboard of the present invention have a low moisture vapor transmission rate (MVTR), excellent glueability and recyclability.
2. Description of Related Art
Corrugated structures such as containers, boxes and the like are known in the art. Practical corrugated pallets and dunnage supports that work well for their intended purposes, including preferred load bearing strength, recyclability, cost effectiveness and simplicity in construction are not known. Additionally, a corrugated assembly that can serve both as a pallet and dunnage support is not known, although such a construction would be useful. Structural characteristics, including weight bearing and cushioning specifications, useful in the production of a novel corrugated pallet design translate quite naturally into a novel corrugated dunnage support, as both assemblies perform similar functions. In an over simplistic description, the pallet of the present invention can be used as a dunnage support when placed between transported products. The pallet can be stood on edge between the products to provide a cushioned barrier the thickness of the pallet.
Referring specifically to the pallet, it is primarily used as a method of handling materials in large quantities. Pallets typically comprise a flat, elevated surface to support containers or packages a sufficient distance from the floor to permit the forks of a forklift to be inserted under them so that the pallet supporting the load can be moved from place to place. For the purpose of transporting products, using pallets to carry goods provides a simple, economical and efficient method. Goods can be stacked onto pallets that will then be handled by forklifts. In so doing, a lot more goods can be carried in each transporting trip to save human labor and to easily load goods to appropriate places.
Most pallets have been and presently are made of wood. In the past, the majority of pallets were constructed specifically of softwood. Of the available materials prior to a new technology in paperboard construction being developed, softwood provided the best balance of both strength and cost.
However, a number of problems face users of conventional wooden pallets. The cost of making and repairing wooden pallets is rising at a rate that is detracting from the cost effectiveness of palletized shipment. Moreover, empty wooden pallets require substantial space for storage, and it is especially costly to transport empty pallets by rail or truck for reuse.
In an effort to reduce costs, many wood pallet producers have resorted to using lower grades of unseasoned or untreated lumber commonly known as "pallet lumber". Pallet lumber typically has a rough finish and is prone to cracking, warping or the like. Further, such rough finishes present a splinter hazard and are unsuitable for some uses, including food-handling applications. Such low grades of lumber also readily split or break, resulting in pallet failure.
Conventional types of pallets must be returned to the shipper after use so the shipper can reuse them, if possible, or the pallets have to be disposed of in a proper manner. Yet, wood pallets are bulky which makes them inconvenient to store and return to the shipper. Damaged wooden pallets generally can not be taken to a landfill or other waste disposal site. Rather, they must be reduced either by chipping or burning before disposal. Chipping is a significant problem inasmuch as nails and other metal fasteners must be removed from the pallet wood before the chipping operation can be undertaken, adding significant cost to pallet reduction. By the same token, increasingly stringent environmental regulations often preclude the burning of used pallets.
Disposal of the conventional wood and nail pallets is a more serious problem when such pallets are exposed to chemical or biochemical materials that contaminate the pallet, since contaminated parts of the pallet can not be destroyed through incineration. The contaminated parts of the pallets often must be disposed in a hazardous waste landfill, which disposal is also inconvenient and expensive.
As forest resources also have been declining in recent years, pallets constructed of plastic and metal have been developed. While it is true that higher pressure-resistant strength is an advantage of pallets made of plastic and metal, in terms of environmental protection these two other types of pallet material no longer meet the requirements of environmental preservation. Additionally, the heavier pallet materials of plastic and metal pallets do not satisfy economic efficiency when weight is the basis for the calculation of transportation costs. After they are made, the finished products of plastic and metal pallets occupy larger spaces and result in much higher storage and transportation costs than do those made of wood.
Thus, there has been a long felt need for a pallet that is lightweight, inexpensive, strong, and has smooth outward surfaces, which pallet is formed of an alternate material other than wood, plastic or metal.
A demand presently exists for recyclable materials such as corrugated paperboard boxes that may be readily remanufactured into recycled corrugated paperboard. Recyclability provides future cost efficiencies on a large scale. Paperboard is a largely homogenous material (with the exception of minor amounts of adhesive and printing ink, which are acceptable in the recycling process) and may be readily collected at a number of discrete sites (e.g., warehouse, factory, retail store, or the like). In some instances, pallets are used to support a number of corrugated containers (e.g., boxes) which may be attached to the pallet using suitable means (e.g., strapping, shrink-wrap or the like). Thus, it is desirable to provide a pallet that can be recycled in the same material stream as its accompanying corrugated containers.
There have been a variety of attempts over the years to replace wooden pallets with those constructed of paperboard. However, past paperboard pallets were not as sturdy as wooden pallets and none of them received widespread acceptance. In recent years, attempts also have been made to replace the bulky and expensive wooden pallets with corrugated paperboard sheets called slip-sheets. These slip-sheets simply comprise a sheet of corrugated paperboard that is slightly larger than the dimensions of the goods to be stacked thereon. The slip-sheet is neither intended for nor capable of supporting the weight of the stacked goods, and must always be supported on a suitable horizontal surface. By providing an extra marginal edge of corrugated board material, it is possible to grasp and slide the sheets and the goods carried thereon about the floor or onto a specialty designed lift truck.
While slip-sheets have provided cost savings in many industrial situations, they simply are not suitable to fully replace palletized shipments. For example, difficulties have been encountered where heavily loaded slip-sheets are positioned directly adjacent the doorway of a fully loaded boxcar or truck trailer. When so positioned, the lift truck mechanism is unable to grasp a sufficient portion of the slip-sheet to pull it onto the lift truck. A slip-sheet improperly grasped is often ripped. This has necessitated, in many situations, unloading the sheet to move the goods out of the carrier and then restacking the goods on the sheet for transport by a lift truck.
An all-corrugated paperboard pallet is very desirable as it can be recycled along with any corrugated containers carried on the pallet. In warehouses and retail stores (e.g., mall or the like) it is known to provide a separate compactor for compacting and storing corrugated waste. Such waste can then be retrieved and recycled into new corrugated material. In addition to the designs noted above, several attempts have been made by others to produce an all-corrugated paperboard pallet by mimicking the design of a wood pallet, using layers of corrugated paperboard in place of wood boards. Such pallets are heavy and expensive as they attempt to achieve the equivalent strength of a wood pallet, which pallet can comprise several layers of corrugated material (e.g., as many as 16 layers).
Another requirement of a practical pallet design is that the pallet be suitably moisture and water resistant. Water spills, rain and condensation may be present in warehouses, loading docks, trucks, railcars, and the like. In many instances a pallet may be placed in proximity to a location where a risk of flooding may occur leaving the pallet placed in a small amount of standing water. Corrugated paperboard pallets of the prior art are not suitably equipped to sustain such moisture conditions. Moreover, alternative pallet designs of paper core, wood and paper pulp will often disintegrate under such conditions.
A novel corrugated paperboard pallet design is desired that that is capable of overcoming the numerous disadvantages of the conventional pallet, and be made from a converted or remanufactured paper product. In most applications, the corrugated paperboard is a layered structure that is usually die-cut to form corrugated structures. It consists of a fluted corrugated medium sandwiched between sheets of linerboard. The simplest three-ply structure is known as "double face." As recently as 1990, much of the linerboard was made entirely from virgin, long-fibered, softwood, kraft pulp. Today, however, these board grades contain sizeable portions of recycled old corrugated containers (OCC) and many are made from 100% OCC.
Around the country, and even in the rest of the world, landfill space for waste disposal is rapidly reaching capacity. By the year 2000, paper and paperboard products are projected to represent 40.9 percent of the municipal solid waste stream and may climb to nearly 42 percent by 2010. New governmental regulations and the public's increasing concern for the environment have created pressure to remove these materials from the solid waste stream. The most widely utilized method of reducing paper waste is recycling.
OCC has a history of efficient recycling use. Even before the era of government mandates and self-imposed industry goals, almost 50% of OCC was recycled in North America. Today's recovery rate is about 62%. It is expected that a level of 70% will be achieved by the year 2000. Today, most of this recycled material goes directly from retail chain stores and factories to mills based on long-term contracts. The rest comes from municipal curbside collection and wastepaper dealers. Some OCC is used in the production of boxboard, and some is even bleached and used in the production of fine paper, but most OCC is used again to produce corrugating medium and linerboard. "Repulping" refers to any mechanical action that disperses dry or compacted pulp fibers into a water slush, slurry or suspension. The action can be just sufficient to enable the slurry to be pumped, or it can be adequate to totally separate and disperse all the fibers. In a typical recycling process, bales of OCC are fed into a repulper where the material is disintegrated and the gross contaminants are removed. The resulting stock is pumped through pressure screens and cyclonic cleaners to remove oversized materials and foreign matter. Reverse cleaners remove plastics, STYROFOAM.RTM. or other lightweight contaminants. The glue, staples, wax, and tapes originally used to assemble the corrugated box must be removed.
Untreated OCC usually creates no problems for recycling. However, paperboard is often treated or coated to enhance its performance and these coatings render the paper unrecyclable. For example, corrugated paperboard is often treated with a curtain coating, wax impregnation, lamination, sizing, or a water-based coating to reduce abrasiveness and to provide for oil and moisture resistance. Moisture vapor transfer rate (MVTR) is a scientific measurement used to describe a product's ability to allow moisture vapor to pass through it, over a specific time period, at a controlled temperature and at a designated atmospheric pressure. While coatings such as wax enhance the moisture resistant properties of the paperboard, the wax coating process is expensive and often renders the paperboard unrecyclable.
In pallet construction, excessive moisture gain can cause a corrugated paperboard pallet to lose its integrity and fail during use, which potentially could lead to heavy economic losses. Traditional solutions generally involve plastic film, either as a laminate with the paperboard or as a bag around the pallet. Both solutions are expensive or incur added labor costs, and greatly reduce or eliminate the recyclability of the pallet. Therefore, there exists a need in the art for coatings that can provide the high moisture resistance needed without compromising the recyclability of the pallet.
The MVTR of a corrugated paperboard pallet is dependent not only upon the coating on the paperboard, but also the method by which that coating is applied. Traditional methods of coating application, such as a rod coater or a blade coater, may result in variations in coating thickness that will cause variations in the MVTR of the coating. The typical solution to this problem has been to merely increase the amount of coating applied to the paperboard. This solution can be expensive and does not result in a consistently coated product both linearly and across the paperboard web.
Referring now to conventional dunnage supports, dunnage support assemblies are frequently employed when transporting industrial articles from one location to another. Known dunnage support assemblies typically comprise a dunnage support member that is secured to a rigid frame. The dunnage support member, itself, is formed of an elastomeric material and has a surface which is adapted to engage and support the dunnage for transportation. The elasticity of the dunnage support member, of course, protects the dunnage from damage that might otherwise result from jarring and vibration of the dunnage during transport.
There have been a number of previously known shipping containers for dunnage, specifically shipping containers for heavy industrial components, such as automotive engines. These previously known shipping containers typically comprise a frame constructed of a rigid material, such as tubular steel. Furthermore, each container is usually designed to transport a number of the industrial components.
Typically, these elastomeric dunnage support members are formed from polyisocyanate that reacts with a resin. The reaction itself is carried out within a mold so that the mold, which conforms in shape to the dunnage support member, forms the part in the desired final shape. Such dunnage support members further can be custom fabricated for the particular dunnage to be transported.
The disposal of previously known dunnage supports after their useful lie, however, presents problems, not unlike the problems associated with damaged wood and plastic pallets. The elastomeric material formed by the reaction of polyisocyanate and resin cannot be recycled and, instead, must be disposed of in a landfill or an equivalent. Such disposal is not only expensive, but also presents potential hazards to the environment.
United States industry has been moving toward the elimination of foam dunnage supports and packaging comprising polystyrene and other foams, principally because of adverse environmental impacts of such type packaging, and accordingly, efforts are directed toward providing a dunnage support that is recyclable. Industries utilizing dunnage supports are varied, and span from the furniture industry to the automobile industry. Any product that is shipped can be protected from scratches, dents and other forms of damage by some sort of dunnage support assembly.
The elastomeric material formed for use as a dunnage support generally is an isomeric material that is spongy. Consequently, once the products are wedged between spaced-apart dunnage support members, the spongy elastomeric material compresses slightly and cushions the dunnage. Another disadvantage of the conventional dunnage support assembly is that the shipping container is often subjected to high impact during transport. This is especially true when train transports the shipping container. In such situations, the spongy dunnage support members have been known to crumble or otherwise abrade during transport. Such abrasion or crumbling of the elastomeric material is unacceptable since it can result in damage to the dunnage.
Thus it can be seen that there is a need for a force resisting corrugated structure that upon construction can be used both as a pallet or a dunnage support, which corrugated structure comprises corrugated board that is capable of minimizing both environmental pollution and transportation expenses, occupying little space before it is configured, and effectively saving production and storage costs. Preferably, the corrugated paperboard pallets and dunnage support assemblies of the present invention have a low moisture vapor transmission rate, excellent glueability and recyclability. It is to the provision of such corrugated structures that the present invention is primarily directed.